Phenol-novolacs with improved optical properties

ABSTRACT

The specification discloses a method for the manufacture of a fluorescent polyphenolic product with high UV absorbance, its subsequent epoxidation, polyphenolic products, epoxidized derivatives and compositions thereof as well as laminates containing fluorescent polyphenolic products and derivatives thereof. The polyphenolic products are prepared by heating glyoxal at a temperature of about 80° C. to about 100° C. with a molar excess of a phenol in the presence of an acidic catalyst which is eliminated from the reaction mixture at a temperature below about 170° C. The total mole ratio of glyoxal to phenol charged to the reaction mixture is about 0.15 to 0.22 moles of glyoxal for each mole of phenol. The glyoxal is added continuously or by stepwise additions to the phenol so as to keep the aldehyde units in the reaction mixture to less than about 70% of the aldehyde units in the total quantity of glyoxal to be charged for making the polyphenol. Water is distilled stepwise or continuously from the reaction mixture. The catalyst is removed from the reaction mixture by further distilling the reaction mixture, generally at higher temperatures. After removal of the catalyst, unreacted phenol is removed by distillation and the reaction mixture is heated at a temperature of about 175° C. to 200° C. for about 0.25 hours to about 3 hours to produce a polyphenolic reaction product having high fluorescence, high UV absorbance and high solubility in organic solvents. The polyphenolic reaction product can be epoxidized by conventional means and such epoxy products used in the manufacture of laminates, coatings and adhesives.

This application is a continuation-in-part of my U.S. patent applicationSer. No. 09/158,584 which was filed on Sep. 22, 1998, now U.S. Pat. No.6,001,950.

This invention relates to phenolic-glyoxal condensates, glycidylatedderivatives thereof, compositions containing the condensates and theirglycidylated derivatives, laminates of reinforcing fibers in a resinmatrix containing epoxidized phenol-glyoxal condensation products orresidues of such products, as well as methods for manufacture of theforegoing.

In the methods for making the condensates of this invention, a molarexcess of phenol is reacted with glyoxal at a temperature of about 80°C. to 100° C. using an acid catalyst which can be removed from thereaction mixture by distillation at a temperature below that of about170° C.

The reaction is conducted by making continuous or at least two additionsof glyoxal to a phenol wherein the total molar ratio for all additionsof glyoxal to phenol is about 0.15 to 0.22. Water in the reactionmixture is removed incrementally by distillation during the reaction.

Less than about 70% of the total glyoxal to be reacted with the phenolis added to the reaction mixture at any one time. Also, less than about70% of the total aldehyde units to be supplied to the reaction mixturetogether with any ketone units formed in the reaction are present in thereaction mixture at any one time. Each glyoxal molecule contains twoaldehyde units. A way for measuring the aldehyde units together with anyketone units formed is by determining aldehyde equivalents, as laterdefined. The aldehyde equivalents in the reaction mixture are maintainedat less than about 70% of the aldehyde equivalents in the total quantityof glyoxal to be charged to the reaction mixture for making thecondensation product. The catalyst is removed from the reaction mixturewhen at least about 85% of the aldehyde equivalents or aldehyde units inthe total quantity of glyoxal to be charged to the reaction mixture formaking the condensation product have reacted. Removal of the catalystalso eliminates all or a portion of the water in the reaction mixture.After about 85% of the said aldehyde equivalents have reacted and priorto removal of the catalyst, in those cases where trichloroacetic acid isthe catalyst, a sufficient quantity of a basic material is added to thereaction mixture to neutralize HCl to be liberated by thetrichloroacetic acid. After removal of the catalyst, the reactionmixture is heated at a temperature of from about 175° C. to 200° C. forabout 0.25 hours to 3 hours. Also, after removal of the catalyst, anyremaining unreacted phenol as well as water is removed at temperaturesabove that used for removal of the catalyst.

Broadly, the laminates of this invention are prepared by the use ofconventional methods and ingredients but with the use of smallquantities of the phenol-glyoxal condensates or reaction productsthereof such as, glycidylated, or epoxidized derivatives as part of theresinous matrix in which fibers are embedded.

BACKGROUND AND PRIOR ART

Polyphenols, such as polyphenols prepared from the condensation ofglyoxal and a molar excess of phenol in the presence of an acidcatalyst, find utility in the same manner as other polyphenols andparticularly for preparing epoxidized polyphenols which can be used forcoatings and electronic applications as well as adhesives and laminatessuch as in the production of printed circuit boards.

The polyphenols of this invention will typically contain from about 1%to about 6% of the tetraphenols of ethane. When the phenol is phenolitself, the tetraphenol is tetrakis(p-hydroxyphenyl) ethane which isalso referred to as TPE. Although the reaction products of thephenol-glyoxal reaction are mixtures, individual polyphenols such as TPEas well as other components thereof can be crystallized out of solutionby conventional techniques. Thus, the level of tetraphenol ethanes, suchas TPE in the phenol-glyoxal condensation products, can be greatlyreduced to essentially zero by methods well known in the art withoutsacrifice of desirable optical properties provided by this invention.Illustratively, use of solvents such as alcohol-aromatic hydrocarbonmixtures and water miscible ketone-water mixtures are effective in thisregard.

The compositions of this invention are particularly useful whenautomatic optical inspection (AOI) is used for quality control oflaminates. The polyphenols of this invention alone, or in blends withphenolic novolacs, or after epoxidation of the polyphenols, are usefulfor AOI as are adducts with epoxy resins and adducts of epoxidizedphenolic-glyoxal condensates with phenolic novolacs. The AOI istypically performed by measuring: fluorescence at wavelengths in therange of about 450 nm (nanometers) to about 650 nm, particularly at anexcitation wavelength of about 442 nm; and/or ultraviolet (UV) lightabsorbance in the wavelengths of from about 350 to 365 nm.

Applicant has found a set of process conditions together with monomersand certain catalysts for obtaining polyphenols and epoxidizedderivatives thereof having UV absorbance and/or fluorescence which issubstantially higher than phenol-glyoxal condensates prepared by othermethods within the wavelengths generally used for AOI quality control.Photoimageable materials are used in conjunction with these condensates.High UV absorbance is desirable for the manufacture of laminates used inelectronic applications such as high density multilayer printed circuitboards.

Advantages of this invention include:

(a) preparation of an essentially metal ion-free polyphenol withoutrecourse to catalyst filtration or neutralization and water washingsteps wherein recovery of phenol is simplified and the reactor yield isincreased in those cases where the catalyst is not neutralized with ametal ion; (b) preparation of polyphenols as well as the epoxidizedderivatives thereof which exhibit improved optical properties, e.g.,high fluorescence and/or UV absorbance in the wavelengths used for AOI;and (c) preparation of polyphenols with increased solubility in organicsolvents.

The prior art discloses many methods for making polyphenols andepoxidized derivatives thereof. But the prior art does not use thecombination of monomers, reaction conditions, or catalyst whichapplicant uses for obtaining the desirable properties of the products ofthis invention. Also, the prior art does not disclose phenol-glyoxalcondensates having the desirable optical properties of this invention.

As used herein, the following terms have the following meanings:

(a) “phenol-glyoxal condensation product” shall refer to thephenol-glyoxal reaction product produced by the method of this inventionwherein such condensate contains less than 5% of unreacted phenol,preferably less than 3% of unreacted phenol and particularly less than1.5% of unreacted phenol.

(b) “aldehyde equivalents” is a method for measuring aldehyde units andshall refer to aldehyde and any ketone units which may be formed in thereaction mixture or in the glyoxal charged or to be charged whenmeasured by the below described method. Such measurements are generallyreported in percent of aldehyde equivalents reacted in comparison withthe aldehyde equivalents charged or to be charged to the reactionmixture. Thus, if measurements of aldehyde equivalents in a mixture ofthe glyoxal and phenol charged show X aldehyde equivalents andmeasurements after reaction in the reaction mixture later show aldehydeequivalents of ½ of X, then the aldehyde equivalents in the reactionmixture are 50% of that charged. During the reaction, some ketone groupsmay also be formed which are included in measuring of the aldehydeequivalents and are considered as part of the aldehyde equivalentsherein.

The method for determining aldehyde equivalents is by taking 1.0 gram ofreaction mixture and diluting it with 50 ml of methanol. The pH is thenadjusted to 3.5 with dilute sodium hydroxide. There is then added, tothe pH adjusted sample, 25 ml of 10% hydroxylamine hydrochloride withstirring. The sample is stirred for 10 minutes and then the sample isback titrated with 0.25 Normal (N) sodium hydroxide to pH of 3.5. Thenumber of milliliters (mls) (the titre) of the sodium hydroxide solutionused to back titrate the sample to a pH of 3.5 is used to calculate thealdehyde equivalents. The mls of sodium hydroxide solution in the titreis adjusted by correcting by titration with sodium hydroxide for themethanol and hydroxylamine hydrochloride reagents used in the test andthis is referred to as the mls blank.

The aldehyde equivalents for the sample are then determined by thefollowing formula: (2.9 times 0.25 N times (mis sodium hydroxide titreminus the mls of the sodium hydroxide in titrating the blank). The valueobtained by this formula is then compared to the aldehyde equivalentsobtained by the above method and formula based on one gram of anunheated, catalyst free mixture of phenol and glyoxal in the weightratio of glyoxal to phenol used until that time or the time in questionin order to determine the percent aldehyde equivalents reacted.

Unless otherwise indicated, the fluorescence measurements herein are asthe maximum counts per second for a 0.05% solution of the material inquestion dissolved in tetrahydrofuran (THF) at an excitation wave lengthof 442 nm for an acquisition time of one second with a CM 1000instrument when measured within the range of about 450 to 650 nm. CM1000 refers to Cure Monitor 1000 which is an instrument made by SpectraGroup Ltd., Inc. of Maumee, Ohio. Acquisition time is the exposure timeat the designated wavelength. A count is a basic unit used by a largenumber of light measuring devices for data output and refers to aprocess of digitization of accumulated signal. In the case of a CCDdetector that is used by Spectra Group Limited, Inc. of Maumee, Ohio andwhich was used for the data set forth herein, light produces anelectrical charge on the detector that is subsequently read out by adigitizer. The digitizer is set to record one count for approximatelyevery 10 units of charge (electrons) it reads.

The fluorescence measurements are on a comparative basis among thevarious materials such as in each of the tables set forth herein and notas absolute numbers. Thus, the fluorescence values of polyphenols withinany one of the tables set forth later herein are relative to otherpolyphenols within the same table, but comparisons cannot be made withthe same or other polyphenols in other tables.

The UV absorbance values are obtained from samples prepared bydissolving the material in question in THF (tetrahydrofuran) at aconcentration of 10 mg (milligrams) per 100 ml (milliliters) and theabsorbance measurement made at 350 nm or 365 nm.

SUMMARY OF THE INVENTION

In one aspect, this invention is directed to a method for preparing apolyphenolic product by incrementally contacting and reacting glyoxalwith a molar excess of phenol in the presence of an acidic catalystwhich can be removed from the reaction mixture by distillation attemperatures below about 170° C. A reaction temperature of about 80° C.to about 100° C. is used for the reaction. Water is removedincrementally from the reaction mixture by distillation while thealdehyde equivalents in the reaction mixture are maintained at less thanabout 70 percent based on the aldehyde equivalents in the total amountof aldehyde to be charged to the reaction mixture in making thepolyphenol. The mole ratio of glyoxal charged to the reaction mixture isfrom about 0.15 to about 0.22 moles of glyoxal for each mole of phenol.The reaction is terminated by distillation to remove the catalyst whenat least about 85% of the aldehyde equivalents in the total quantity ofglyoxal to be charged for making the condensation product have reacted.When trichloroacetic acid is the catalyst, a basic material is added tothe reaction mixture prior to removal of the catalyst to neutralize anyhydrochloric acid which may be released during removal of catalyst.Removal of the catalyst also removes some or all of the water in thereaction mixture. After elimination of the catalyst: (a) free orunreacted phenol is distilled out of the reaction mixture so that theproduct is free of catalyst and contains less than about 5% of phenol;and (b) the reaction mixture is heated at a temperature of from aboutabove 175° C. to about 200° C. for 0.25 to 3 hours.

In another aspect, this invention is directed to a method of preparing apolyphenolic product which comprises: charging and reacting phenol, andabout 0.06 to 0.11 moles of a 40% solution of glyoxal in water in thepresence of about 2 to 5% of oxalic acid, the moles of glyoxal based onthe moles of phenol charged; distilling the reaction mixture a firsttime to remove about 8% to 12% of distillate after about 1 to 5 hours ofreaction time; charging another 0.06 to 0.11 moles of glyoxal based onphenol charged so that the total quantity of glyoxal charged is fromabout 0.15 to 0.22 moles for each mole of phenol; continuing thereaction for about another 1 to 5 hours from the time the firstdistillation was commenced, and distilling the reaction mixture a secondtime to recover about 6% to 12% of distillate; and continuing thereaction until at least about 85% of the aldehyde equivalents in thetotal quantity of glyoxal to be charged for making the condensationproduct have reacted. The above temperature of phenol reaction withglyoxal, including the distillations, is 80° C. to 100° C. After atleast about 85% of the aldehyde equivalents have reacted as discussedabove, the temperature is raised and the reaction mixture is distilledat a temperature within the range of about 130° C. to about 170° C. toremove catalyst and water. Unreacted phenol remaining after removal ofthe catalyst is removed by distillation at temperatures above those usedfor removal of the catalyst so that the free phenol in the polyphenolcondensate is not more than about 5% and the reaction mixture is heatedunder vacuum at a temperature of about 175° C. to 200° C. for about 0.25to 3 hours to produce the phenol-glyoxal condensation product.

In a further aspect, this invention is directed to a method forpreparing epoxy resins in the form of glycidyl ethers of the abovedescribed polyphenols by epoxidizing the polyphenol with a halohydrin inthe presence of an alkali metal hydroxide, e.g., sodium hydroxide.

In a still further aspect, this invention is directed to a method forpreparing epoxy resins by reacting the phenol-glyoxal condensationproduct with a preformed epoxy resin to prepare epoxy resin derivativesof the phenol-glyoxal condensation products.

In yet other aspects, this invention is directed to the polyphenolsprepared by the methods of this invention and epoxidized productsprepared therefrom.

In yet further aspects, this invention is directed to compositionscontaining the phenol-glyoxal condensation products or epoxidizedderivatives thereof and compositions with other phenolic novolacs and/orepoxidized derivatives thereof.

In another aspect, this invention is directed to cured or uncuredreaction products of the phenol-glyoxal condensates such as thoseprepared by glycidylation, epoxidation, or reaction with aphenol-formaldehyde novolac resin or a glycidiylated or epoxidizedderivative of a phenol-glyoxal condensate with the novolac resin as wellas laminates of reenforcing fibers or fabrics of such fibers in a resinmatrix containing the phenol-glyoxal condensates and reaction productsthereof.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 of the drawing is a graph showing fluorescence spectra of variousepoxidized products. Letter “A” indicates the fluorescence spectra curveof EPON 1031 (CAS No.: 7328-97-4) which is a commercial epoxy resin of apolyphenol having less than 1% of free phenol which is commercially usedfor AOI fluorescence in the same wave lengths which are shown in thegraph. EPON 1031 is sold by Shell Chemical Co. Letter “B” indicates thefluorescence spectra curve of the epoxidized product of Example 5A ofthis application wherein the epoxidized product is produced by the samemethod as shown in Example 8 herein. Letter “C” indicates thefluorescence spectra of the epoxy product of Example 8.

It can be seen from FIG. 1 of the drawing that the poly glycidyl etherof the phenol-glyoxal condensation product of this invention hasunexpectedly greater fluorescence at an excitation wavelength 442 for anacquisition time of one second when measured within the range of 450 to650 nm in comparison to the commercial product EPON 1031 as well as thepoly glycidyl ether of the product of Example 5A.

DETAILED DESCRIPTION OF THE INVENTION

The Phenolic Monomer

The phenolic monomer, also referred to simply as a phenol, is a phenolwhich can be unsubstituted or substituted, e.g., with alkyl, phenyl oralkoxy groups. Typical phenolic monomers are the mononuclear orbinuclear, monohydroxyphenols which have at least one ortho or paraposition available for bonding.

The phenolic monomer will typically contain up to about 12 carbon atomsand preferably up to about 8 carbon atoms. Such compounds include:phenol itself; alpha-naphthol; phenylphenol; cresols, e.g.,2-methylphenol and 3-methylphenol; various xylenols, e.g.,2,5-dimethylphenol and 3,5-dimethylphenol; and other alkyl phenols; andalkoxyphenols such as 2-methoxy- or 3-methoxyphenol. Mixtures ofphenolic compounds can be used. A preferred phenolic compound isunsubstituted phenol, i.e., phenol itself.

Preferred phenolic monomers can be represented by the following formula:

wherein R′ is selected from phenyl, alkyl of 1 to 4 carbon atoms andalkoxy of 1 to 4 carbon atoms and_(y) is an integer of 0 to 3.

When R′ is alkyl or alkoxy,_(y) is 1 to 3, and when R′ is phenyl,_(y)is 1. Mixtures of the phenolic monomers can also be used.

The Glyoxal Reactant

The glyoxal reactant can be in various forms such as relatively puremonomeric glyoxal, polymerized glyoxal or glyoxal dissolved in water andmixtures thereof. Illustratively, glyoxal is normally used as a 40%solution in water.

The Acid Catalyst

The acid catalyst is one which can be removed from the reaction mixtureby distilling the reaction mixture at a temperature above about 80° C.but below about 170° C. and preferably below about 160° C.Illustratively, the catalyst can be oxalic acid or a trihaloacetic acidor mixtures thereof.

In the case of oxalic acid as catalyst, the temperature of the reactionmixture is raised above about 130° C. such as up to about 170° C.together with distillation and preferably the temperature is raised toabout 140° C. to about 160° C. so that the oxalic acid catalyst isdecomposed to volatile components.

Oxalic acid can be used in its various forms such as the pure compound,the dihydrate, or mixtures thereof, all of which are referred to asoxalic acid herein.

Illustrative of the trihaloacetic acid catalyst there can be mentioned:trichloroacetic acid and trifluoroacetic acid. Trifluoroacetic acid mayneed to be replenished during the reaction since a portion thereofdistills together with the water. Trifluoroacetic acid forms anazeotropic mixture in water. Therefore, when it is desired to remove thetrifluoroacetic acid catalyst, it is preferred that a series ofdistillations be made with the addition of water after each distillationso as to remove substantially all of the acid.

When trichloroacetic acid is used as the catalyst, the temperature israised up to about 170° C. to remove the catalyst after any hydrochloricacid to be formed from the trichloroacetic acid is neutralized.

The quantity of the catalyst can vary from about 1% to about 6% based onthe weight of the phenol charged to the reaction mixture. The quantityof oxalic acid is from about 1% to 6%, preferably about 1.5% to about 5%and particularly about 2.5% to about 4% based on the weight of phenolcharged to the reaction mixture. When a trihaloacetic acid is used ascatalyst, the quantity of catalyst is preferably from about 1% to about4% by weight based on the phenol charged to the reaction mixture andparticularly about 1% to about 3%. Mixtures of the acid catalysts canalso be used.

The Reaction Conditions

The polyphenols (condensation products) of this invention may beprepared by continuous or step-wise contact of the glyoxal with a molarexcess of the phenol in the presence of the acid catalyst.Illustratively, for stepwise reaction, a phenol and the acid catalystare charged to a reactor and then an initial increment of the glyoxal ischarged to the reactor while the reaction mixture is maintained at atemperature of about 80° C. to about 100° C. The glyoxal reacts with thephenol and then additional glyoxal is charged to the reaction mixture.

The molar ratio of glyoxal to phenol in the manufacture of thephenol-glyoxal condensation products is from about 0.15 to 0.22 moles ofglyoxal for each mole of phenol charged and preferably about 0.16 to0.20 moles of glyoxal for each mole of phenol charged. When a total oftwo increments of glyoxal are made to the reaction mixture, it ispreferred that each increment be from abut 0.06 to 0.11 moles of glyoxalbased on the total moles of phenol charged and particularly about 2equal molar quantities of the glyoxal. Total mole ratios of less thanabout 0.15 moles of glyoxal for each mole of phenol charged give more ofthe tetraphenols, such as TPE which is essentially devoid of opticalproperties in the ranges given above for AOI quality control. Ratios ofgreater than about 0.22 moles of glyoxal for each mole of phenol lead tolonger reaction times and are likely to give product with higherviscosity.

The aldehyde equivalents or aldehyde units in the reaction mixture aremaintained at less than about 70%, and preferably less than about 60% ofthe total aldehyde equivalents or aldehyde units which will be chargedto the reaction mixture for making the phenol-glyoxal condensate. Thus,not more than about 70% of the aldehyde equivalents to be used in thereaction are present in the reaction mixture at any one time.

The catalyst is removed from the reaction mixture after at least about85% of the aldehyde equivalents of the total aldehyde equivalents to becharged to the reactor have reacted, and preferably when from about 90%to 95% of such aldehyde equivalents have reacted. Then the temperatureis generally raised to remove the catalyst. However, whentrichloroacetic acid is the catalyst, a basic material is added to thereaction mixture in an amount sufficient to neutralize any hydrochloricacid to be formed as a decomposition product of such acid beforedistillation is effected to remove the catalyst.

When the basic material used to neutralize hydrochloric acid is analkali metal oxide or hydroxide or an alkaline earth metal oxide orhydroxide, e.g., sodium hydroxide or calcium hydroxide about 80% molarequivalents of such base are added based on the molar equivalents of thetrichloroacetic acid used as catalyst. When an amine is used as thebasic material, about 10% to 20% of the amine molar equivalents areadded to the reaction mixture for neutralizing HCl based on the molarequivalents of trichloroacetic acid used as catalyst. It is preferredthat the basic material be an amine so that metal ions such as that ofalkali metal or alkaline earth metals not be included in the product.The presence of metal ions is deleterious for use of the product in themore demanding electronic applications. Illustrative of amines forneutralizing the hydrochloric acid there can be mentioned amines havinga pKa value of about 5 to about 11 such as pyridine, picoline,benzyldimetylamine, triethylamine, and hydroxyethyidiethylamine.

The total time for the condensation reaction of aldehyde with the phenolwill typically vary from about 5 to about 15 hours and preferably about8 to 12 hours.

The temperature of the condensation reaction of the phenol and glyoxalin the presence of the catalyst, including distillations, will be in therange of from about 80° C. to about 100° C. and preferably from about85° C. to 95° C. until at least about 85% or more of the aldehydeequivalents in the total quantity of glyoxal to be charged for makingthe condensation product have reacted.

Water is removed continuously or intermittently by distillation, such asafter the reaction of glyoxal with phenol following individual additionsof the glyoxal, since accumulation of water in the reaction mixtureslows the reaction. Water is formed by the condensation reaction ofglyoxal with phenol and additionally water is generally present in theglyoxal charge, e.g., glyoxal is generally used as a 40% solution inwater.

The water content in the reaction mixture is preferably kept to belowabout 8% by weight based on the phenol charged to the reaction mixtureand preferably below about 6% based on the weight of phenol charged tothe reaction mixture. Illustratively, two or more, e.g. 2 to 4,additions of the glyoxal are made to the reaction mixture withdistillation of water after reaction of glyoxal with the excess phenol.Preferably, an initial glyoxal charge is made with the subsequentreaction followed by distillation of water and then a second glyoxalcharge is made followed by reaction of the monomers prior to reacting atleast about 85% of the total aldehyde equivalents to be used for makingthe condensation product.

Instead of monitoring the progress of the reaction by measuring aldehydeequivalents, the time of reaction can be used for conducting thereaction when the reactants and catalysts are the same and the operatingconditions are within the same ranges, e.g., mole ratios, reactiontemperatures, the catalyst and the quantity thereof; times fordistillation of water and the amount of distillate. Illustratively, thefollowing steps and time periods can be used when: total molar ratio ofglyoxal to phenol is from about 0.15 to 0.22; a 40% solution of glyoxalis reacted with phenol itself at a temperature of 80° C. to 100° C.; aninitial glyoxal charge is made with subsequent reaction of the glyoxalwith phenol and in time by distillation, followed by another glyoxaladdition followed by continued reaction and then distillation which isfollowed by continued reaction before depletion of the aldehydeequivalents to 15% or less of that charged. From about 0.06 to 0.11moles of the glyoxal, based on the amount of phenol charged, are addedwith each charge of the glyoxal. Thus, after addition of the initialquantity of glyoxal, the aldehyde is reacted with the phenol for about 1to 5 hours, preferably 1.5 to 3 hours and then there is distilled fromabout 8% to 12% of a first distillate from the reaction mixture based onthe weight of phenol charged.

After the first distillation, which is also conducted within thetemperature range of about 80 to 100° C. another 0.06 to 0.11 moles ofglyoxal based on the moles of phenol charged, are slowly added to thereaction mixture. Preferably, there is charged about equal quantities ofglyoxal during each addition. Heating of the reaction mixture iscontinued for another 1 to 6, preferably 1.5 to 5 hours from the timethe first distillation commenced and then a second distillation isstarted to remove about another 4% to 12% of water based on the phenolcharged. After the second distillation, the reaction is permitted tocontinue for another 0.5 to 6, preferably 1 to 4 hours from the time thesecond distillation commenced before the temperature is raised fordistillation together with removal of the catalyst.

The temperature of 80° C. to 100° C. is used until it is time to raisethe temperature and remove the catalyst or unreacted phenol. Suchdistillation, prior to increasing the temperature for removal ofcatalyst, is conducted under vacuum so as to assist in the control ofthe temperature. The vacuum can vary from about 15 to 25 inches or moreof mercury.

The temperature for removal of the catalyst by distillation is less thanabout 170° C., preferably less than about 160° C. When oxalic acid isthe catalyst, the temperature is raised above 135° C. to about 170° C.,particularly about 155° C. to about 160° C.

All or some of the water is removed at the time the catalyst is removed.In the case where oxalic acid is the catalyst, all or substantially allof the water is removed when the catalyst is removed from the reactionmixture. Any water remaining in the reaction mixture after eliminationof the catalyst is finally removed by the distillation in removal of thephenol.

After removal of the water and all of the catalyst, unreacted (free)phenol is removed from the reaction mixture so as to bring the freephenol content of the reaction mixture to less than about 5%, preferablyto less than about 2% and particularly less than about 1.5% by weight ofthe reaction mixture.

Removal of the unreacted phenol is attained by conventional means suchas in the removal of unreacted phenol in novolac resins, e.g., flashdistillation by heating the reaction mixture at an elevated temperatureunder vacuum. Thus, the temperature can be up to about 190° C. or 200°C. under about 25 to 30 inches of mercury. Steam sparging under vacuumat such temperatures can also be used to remove phenol in the product.

Concurrently with removal of phenol or as a separate step followingremoval of the catalyst, the reaction mixture is heated at a temperatureof from about 175° C. to about 200° C. and preferably from about 180° C.to about 195° C. Such heating is conducted for a period of about 0.25 to3 hours and preferably for about 0.5 to 2 hours. All or a portion ofsuch heating can be conducted at the time the phenol is removed undervacuum. Optionally, the phenol-glyoxal condensation product with 5% orless of unreacted phenol can be placed in an inert atmosphere and heatedto conduct a portion or all of the heating in the range of about 175° C.to 200° C. for about 0.5 to 3 hours. Illustrative of an inert atmospherethere can be mentioned nitrogen or argon. After such heating step atabout 175° C. to 200° C. and reduction of phenol in the reaction mixtureto less than 5%, the reaction mixture is also referred to as thephenol-glyoxal condensation product.

The phenol-glyoxal condensation product is eventually cooled andgenerally comminuted, e.g., flaked.

The Phenol-Glyoxal Condensation Products

Properties of the phenol-glyoxal condensation products are as follows:

Broad Preferred Property Range Range Mw/Mn 400-600/300-390440-540/320-370 Viscosity, 300-2500 450-1500 cps at 175° C. Free Phenol(%) 0-5  0.03-1.5  Tetraphenol ethane 0-6  1-4  such as TPE (%) UVabsorbance at at least 0.400 at least 0.450 350 nm particularly >0.5 UVabsorbance at at least 0.260 at least 0.275 365 nm particularly >0.30

Fluorescence: The fluorescence of the phenol glyoxal condensates isabout 70% higher at fluorescence maximum (about 532 nm) than AcridineOrange Base (Aldrich Chemical) using an excitation wavelength of 442 nm,acquisition time of 0.5 seconds as measured in a CM 1000 instrument(Spectra Group Ltd, Inc. of Maumee, Ohio). Acridine Orange Base was usedat a concentration of 0.2 mg per liter in methanol and thephenol-glyoxal condensate at a concentration of 0.05 weight percent intetrahydrofuran. The Acridine Orange base of Aldrich Chemical isdescribed on page 33 of the Aldrich Chemical catalogue which is dated2000-2001.

The phenol-glyoxal condensation products contain a variety of compounds,including polyphenols such as di-, tri-, and tetraphenols.Illustratively, such tetraphenols can be represented by the formula:

wherein _(x) is an integer of 0 to 3. When R is alkyl and or alkoxy _(x)is 1-3 and the alkyl and alkoxy groups have 1 to 4 carbon atoms. Whenthe reactants are phenol itself and glyoxal, the above polyphenol istetrakis(4-hydroxyphenyl)ethane (TPE) which is also referred to as1,1,2,2-tetrakis(4-hydroxyphenyl)ethane. Epoxidation of thetetrakis(4-hydroxyphenyl)ethane gives the tetraglycidyl ether oftetrakis(4-hydroxyphenyl)ethane.

If 10 grams of a phenol-glyoxal condensate are reacted with 40 grams ofan epoxide, the amount phenyl-glyoxal condensate residue of thecomposition would be 10 grams. Also, if 20 grams of a phenol-glyoxalcondensate is glycidylated and the glycidylated product is subsequentlyreacted with a phenol-formaldehyde novolac, the amount phenol-glyoxalresidue would still be 20 grams.

The epoxy resin used in the laminate compositions of this invention willhave a weight per epoxide (WPE) value of from about 190 to 10,000 andpreferably from about 190 to 500.

The pressure used in making the laminates can vary from the contactpressure of applying a laminated lining to a tank wall to the highpressure, e.g., 1,000 psi or more, used in the manufacture of electricalinsulation sheets. The temperature used in making the laminates can varyover a wide range such as that of about room temperature to over 210° C.

The use of a solvent in the laminate compositions is optional.

Preparation of Polyepoxides

Epoxidized products of the phenol-glyoxal condensates can be prepared byat least two different conventional routes. One route is by reaction ofthe phenol-glyoxal condensate with a halohydrin in the presence of analkali metal hydroxide to form glycidyl ethers of the polyphenol. Suchepoxidized products will typically have epoxy equivalents of about 190to 230 and preferably about 205 to 225. The other route is by reacting amolar excess of a preformed polyfunctional epoxy with the phenol-glyoxalcondensate. Such epoxidized products by the other route will typicallyhave epoxy equivalents of about 140 to 250 and preferably about 160 to230.

In the first route, the polyepoxide is prepared by contacting thephenol-glyoxal condensation product with an excess of epichlorohydrin inthe presence of an alkali metal hydroxide such as sodium hydroxide orpotassium hydroxide at a temperature within the range of about 50° C. toabout 80° C. Optional catalysts, such as quaternary ammonium salts, maybe employed. The reaction can be carried out in the presence of an inertsolvent, including alcohols such as ethanol, isopropanol, methylisobutyl ketone (MIBK), toluene, ethers, and mixtures thereof.

Another method for preparing the polyepoxide by the first route is setforth in U.S. Pat. No. 4,518,762 of May 21, 1985 to Ciba Geigy Corp.which is incorporated herein by reference in its entirety. Briefly, inthis process, the polyphenol, preferably the phenol-glyoxal purifiedproduct, is reacted at a temperature of 40° to 100° C., in the absenceof any catalyst specific for the formation of the chlorohydrin etherintermediate, in the presence of 2 to 25% by weight, based on thereaction mixture, of a lower alkanol or lower alkoxyalkanol cosolvent,with excess epichlorohydrin, based on the phenolic hydroxy value, in thepresence of 0.5 to 8% by weight of water, based on the reaction mixture,and with 0.9 to 1.15 equivalents of solid alkali metal hydroxide perphenolic hydroxyl group to give the epoxy derivative of the polyphenoland wherein there is 0.5% to 8 % by weight of water in the reactionmixture throughout the reaction period, using a solid alkali metalhydroxide in the form of beads of about 1 mm diameter, which hydroxideis charged to the reaction mixture portionwise or continuously during agradually escalating addition program, and then isolating the epoxynovolac resin.

In the second route for preparation of the epoxy resins containing thephenol-glyoxal condensation products of this invention, one part byweight of such condensation product is reacted with 4 to 8 parts of apolyepoxide at about 100° C. to about 150° C. using a catalyst, e.g.,potassium hydroxide, benzyldimethylamine, benzyltrimethylammoniumhydroxide, 2-methyl imidazole, and2,4,6-tris(dimethylaminomethyl)phenol. Typical catalyst levels are about0.1% to about 0.6% based on the reaction mass. Typical polyepoxides forreaction with the phenol-glyoxal condensation product are those ofdiglycidyl ether resins, e.g., the diglycidyl ether resins of: bisphenolA; bisphenol F; resorcinol; neopentyl glycol; cyclohexane dimethanol;and mixtures thereof.

The phenol-glyoxal condensation products of this invention can also bepartially epoxidized without sacrifice in the desirable opticalproperties by reduction of the quantity of alkali used in the reactionwith epichlorohydrin. Illustratively, reduction of caustic to about 40%to 70% of that in the methods of the above described first route affordspartially epoxidized derivatives.

Unless trichloroacetic acid is used as catalyst with metal ion oxides orhydroxides for neutralization of the hydrochloric acid, thephenol-glyoxal condensation products of this invention will typicallyhave a percent by weight concentration of metal ions of less than about:0.005% for sodium: 0.003% for calcium; 0.003% for iron; and 0.002 % forpotassium.

The phenol-glyoxal condensates can be used alone to cure epoxy resinsbut preferably they are used in combination with other epoxy resincuring agents.

The laminates of this invention are conventional laminates containing areinforcing agent such as glass cloth, and a resinous matrix comprisingan epoxy resin and a curing agent for the epoxy agent such as aphenol-formaldehyde resin, except that the resinous matrix will alsocontain from about 1 to 35 parts by weight, preferably about 1 to 15parts and particularly about 2 to 10 parts by weight, based on theweight of of the resinous matrix, of a phenol-glyoxal condensate,residue or mixture thereof. The epoxy resin, curing agent,phenol-glyoxal condensate or residue thereof and optionally a solventsystem for the epoxy and curing agent, will generally comprise at least75% of the resinous matrix or mixture.

The resinous matrix of the laminates of this invention containing asolvent will generally contain, by weight, from about 40 to 80 andpreferably 50 to 70 parts of an epoxy resin; about 1 to 15 parts andpreferably about 2 to 10 parts of a phenol-glyoxal condensate, residueor mixture thereof about 10 to 35 and preferably 15 to 30 parts of asolvent and about 7 to 35 parts of a conventional epoxy curing agent.

The preferred polyepoxide products of this invention when used inelectronic applications such as laminates for the production of printedcircuit boards will typically comprise the following composition basedon 100 parts of an epoxy resin, e.g., an epoxy resin such as thediglycidyl ether of bisphenol A:

(a) about 18-25 parts of a curing agent such as a phenol-formaldehydenovolac;

(b) about 3-10 parts of a member selected from the group consisting of aglycidylated phenol-glyoxal condensation product, a reaction product ofan epoxy resin and a phenol-glyoxal condensation product, aphenol-glyoxal condensation product and mixtures thereof; and

(c) optionally, an epoxy curing accelerator.

Epoxy resins for laminating and coating formulations are generallysolvent based. Coating formulations may include fillers whereaslaminating formulations generally impregnate multiple layers of a fibermatrix such a glass cloth with a phenolic compatible finish.

The laminates of this invention can be made flame retardant byconventional techniques such as the use of a halogenated epoxy resin asthe main resin matrix ingredient or a brominated or chlorinated flameresistant additive such as chlorinated bisphenol-A, tetrachlorinatiedbisphenol-A or tris (2,3-dibromopropyl)phosphate and antimony oxide.

Conventional laminating techniques can be used in making the laminatesof his invention such as the wet or dry-lay-up techniques.

The laminates of this invention will generally contain about 40% to 80%by weight of resinous matrix material and about 20% to 60% by weight ofreinforcing material such as glass cloth.

Epoxy resins useful in this invention are generally those derived frombisphenol-A and brominated bisphenol A with weight per epoxy (WPE)values of about 190 to about 2,000. Other epoxy resins which may be usedapart from the bisphenol A resins include: epoxy phenol novolacs; epoxycresol novolacs; aromatic glycidyl amine resins such as triglycidyl-p-amino phenol; N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane. Epoxy phenol novolacs include epoxy resins derived fromphenol-glyoxal condensates by reaction with epichlorohydrin, in thepresence of alkali such as Epon 1031 of Shell Chemical; reactionproducts of an epoxy resin and a phenol-glyoxal condensation product.The conventional epoxy resin making up the 100 parts of the compositionis preferably a flame retardant epoxy resin such as a halogenated epoxyresin, e.g., chlorinated or brominated epoxy resin. Illustrative of suchbrominated epoxy resins there can be mentioned the brominated product ofthe diglycidyl ether of bisphenol A, e.g., EPON 1124 (CAS No.:26265-08-07) of Shell Chemical Co. This brominated epoxy resin can beused in flame retardant compositions with epoxy resins such as those ofglycidyl ethers of a phenolic novolac, glycidyl ethers of ano-cresol/formaldehyde novolac, diglycidyl ethers of bisphenol A,diglycidyl ethers of bisphenol F, diglycidyl ethers of resorcinol,diglycidyl ethers of neopentyl glycol or diglycidyl ethers ofcyclohexanedimethanol and mixtures thereof.

Epoxy curing accelerators can be used in a quantity sufficient toaccelerate the cure of the epoxy resin. Generally, such quantity is fromabout 0.05 to 0.5 parts based on 100 parts of the epoxy resin andparticularly about 0.1 to 0.2 parts. Such accelerators include2-methylimidazole, 2-ethyl-4-methylimidazole, amines such as 2,4,6-tris(dimethylaminomethyl)phenol and benzyldimethylamine, andorganophosphorus compounds such as tributylphosphine andtriphenylphosphine.

Reactive diluents may also be present to lower viscosity and improvehandling characteristics. Examples of reactive diluents includeneopentylglycol diglycidyl ether; butanediol diglycidyl ether;resorcinol diglycidyl ether; and cyclohexane dimethanol diglycidylether.

A variety of curing agents well known in the art can be used for theepoxy resin. They include but are not limited to aromatic amines,polyamidoamines; polyamides; dicyandiamide; phenol-formaldehydenovolacs; and melamine-formaldehyde resin.

When phenol novolacs are used as curing agents a catalyst (accelerator)is generally employed and may be selected from tertiary organic amidessuch as 2-alkylimidazoles; N,N-dimethylbenzylamine; and phosphines suchas triphenylphosphine and mixtures thereof.

The phenol novolac curing agents are condensation products of phenolwith formaldehyde wherein the phenol can be selected from phenol itself,cresols, xylenols, resorcinol, bisphenol-A, paraphenyl phenol, naphthol,and mixtures thereof. Substituents for the monomers include hydroxy,alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms as well asphenyl. Novolacs and dicyanodiamides are preferred curing agents.Particularly preferred curing agents are the phenol-formaldehydenovolacs and ortho-cresol-formaldehyde novolacs having a molecularweight of 1,000 to 5,000.

A wide variety of solvents may be used, including haolgenated solvents,ketones, alcohols, glycol ethers, glycol acetates,N,N-dimethylformamide. The later is particularly useful whendicyandiamide is used as curing agent. Ketones include acetone, methylethyl ketone, diethyl ketone, and methyl isobutyl ketone.

Reinforcing fibers or fabrics of reinforcing fibers include glass fibersand mats; carbon and graphite fibers, cellulosic paper, fibrouspolyamide sheets, fibrous quartz sheets, woven fibrous glass cloth,unwoven fibrous glass mat, and the like.

Fillers such as quartz powdered, mica, talc, calcium carbonate and thelike may also be added to the resinous matrix.

The laminate can be prepared at room temperature or by heating underpressure a layer comprising at least one sheet of prepreg comprising anepoxy resin as impregnant.

The weight average molecular weight (Mw) and number average molecularweight(Mn) herein are measured using gel permeation chromatography andphenolic compounds and polystyrene standards. The sample molecularweight to be measured is prepared as follows: the sample is dissolved intetrahydrofuran and the solution is run through a gel permeationchromatograph. Any free phenol in the sample is excluded fromcalculation of molecular weight.

The quantity of TPE in the various reaction mixtures was determined bythe following method.

(a) The reagents used were para-ethyl phenol, TPE, and silylationreagent.

(b) Procedure for determining TPE was as follows:

A silylation reagent was prepared as follows: into 25 ml (milliliter)reaction flask, add by syringe: 10 cc (cubic centimeters) of pyridine, 3cc of trimethylchlorosilane (TMCS), and 10 cc of hexamethyidisilazane(HMDS). This was left to stand for 5 to 10 minutes.

(c) The TPE standard solution is prepared as follows:

Weigh into vial (appropriate for silylation) approximately 30 mg eachTPE and p-ethylphenol. Add 1 cc silylation reagent. Shake untildissolved (approximately 10 minutes). Heat in low temperature ovenovernight. Inject 1 microliter into gas chromatograph. Use methyl ethylketone as rinses. The column used for this analysis is Dexsil 300 whichis supplied by Supelco of Belfonte, Pa.

In order that those skilled in the art may more fully understand theinvention presented herein, the following examples are set forth. Allparts and percentages in the examples, as well as elsewhere in thisapplication are by weight, unless otherwise specifically stated.

The following examples are illustrative of the invention. Some of theexamples are designated as “comparative” to show differences fromexamples which are part of this invention and not necessarily ascomparisons with the prior art.

EXAMPLE 1 PREPARATION OF PHENOL-GLYOXAL CONDENSATION PRODUCT AT 90° C.WITH TWO ADDITIONS OF GLYOXAL AND OXALIC ACID CATALYST

To 1,728 grams (g) (18.36 moles) phenol and 69.1 g oxalic acid dihydrateat 90° C. there was added over 30 minutes 227 g of 40% glyoxal in water(1.57 moles). The temperature was maintained at 90° C. for another 1.5hours and then there was vacuum distilled 185 g of distillate (10.7%based on the weight of phenol charged) from the reaction mixture at 90°C. over a period of forty minutes. After such heating, approximately 79%of the aldehyde equivalents charged until that time had reacted and thequantity of water in the reaction mixture was about 4%. Another 227 g of40% glyoxal in water (1.57 moles) was added to the reaction mixture overa 25 minute period while the temperature was maintained at 90° C. for1.5 hours and then there was vacuum distilled 195 g of distillate (11.3%based on the weight of phenol charged) at 90° C. over a period of thirtyminutes. After such heating approximately 70% of the aldehydeequivalents charged until that time had reacted and the water content ofthe reaction mixture was about 3.5%. The molar ratio of glyoxal tophenol for the total of both glyoxal additions was 0.17. The temperatureof 90° C. was maintained for another 1.5 hours. After such heating, 90%of the aldehyde equivalents charged to the reaction mixture until thattime had reacted and the water content was about 4.5%. Then the reactionmixture was distilled at atmospheric pressure to 160° C. and held at160° C. for one hour. The reaction mixture was then vacuum distilled toremove the bulk of unreacted phenol at 155-160° C. Vacuum distillationwas continued up to a temperature of 190° C. and held at thattemperature for one hour until phenol in the reaction mixture was lessthan 1%. The resulting phenol-glyoxal condensation product was thencomminuted, e.g., flaked. During the reaction the aldehyde equivalentsin the reaction mixture were maintained at less than about 70% of thealdehyde equivalents in the total quantity of glyoxal to be charged formaking the phenol-glyoxal condensation product. Properties of thephenol-glyoxal condensation product are given in tables which follow.

In the tables which follow, this example is also referred to as EX1.

EXAMPLE 2 (COMPARATIVE) PREPARATION OF PHENOL-GLYOXAL POLYPHENOL AT 90°C. WITH ONE ADDITION OF GLYOXAL AND OXALIC ACID CATALYST

To 576 g (6.12 moles) phenol and 23 g oxalic acid dihydrate at 85° C. isadded over a period of about one hour 151.4 g of 40% glyoxal in water(1.04 moles) during which period the temperature was slowly raised to90° C. The mole ratio of glyoxal to phenol was 0.17. Immediatelythereafter, vacuum is applied to remove 120 g of distillate at 90-95° C.over a period of 60 minutes. A temperature of 90-92° C. was maintainedfor 2.25 hours after which time about 82% of the aldehyde equivalentscharged had reacted. Then vacuum was applied over 15 minutes to remove13.3 g of distillate. Heating was continued at 90° C. to 91° C. for 1.25hours. After the 1.25 hour period approximately 88% of aldehydeequivalents charged had reacted. Vacuum was then applied over 6 minutesto remove 6.68 g of distillate. Heating at 90° C. was continued for 5hours and one hour at 100° C. After such heating for one hour, about 94%of the aldehyde equivalents charged to the reaction mixture had reacted.The reaction mixture was atmospherically distilled to 160° C. Thetemperature of 160° C. was held for one hour. The reaction mixture wasthen vacuum distilled to remove the bulk of unreacted phenol at 155-160°C. and the vacuum distillation was continued at 190° C. until phenol inthe reaction mixture was less than 1%. During the vacuum distillationthe reaction mixture was heated at a temperature of about 175° C. to192° C. for about 0.25 hours. The reaction mixture is then dischargedfrom the reactor and then comminuted, e.g., flaked. Properties of thepolyphenol product of this example are given in tables which follow andthis example may be referred to as EX2.

EXAMPLE 3 (COMPARATIVE) PREPARATION OF PHENOL-GLYOXAL POLYPHENOL AT 102°C. AND REFLUX (103-104° C.) WITH ONE ADDITION OF GLYOXAL AND OXALIC ACIDCATALYST

To 576 g (6.12 moles) phenol and 23 g oxalic acid dihydrate at 90° C.there was added over a one hour period 151.4 g of 40% glyoxal in water(1.04 moles) while the temperature was allowed to rise to reflux(103-104° C.). The mole ratio of glyoxal to phenol was 0.17. Thereaction mixture was held at reflux for 10 hours. After such refluxapproximately 89% of the aldehyde equivalents had reacted. Thetemperature was then raised to 110° C. and there was removed 55.5 g ofdistillate over a period of about 22 minutes. The temperature was heldat 110° C. for one hour and then the reaction mixture wasatmospherically distilled to 160° C. The reaction mixture was then heldfor one hour at 160° C. The reaction mixture was then vacuum distilledto remove the bulk of unreacted phenol at 155-160° C. and the vacuumdistillation was then continued at 176° C. until phenol in the reactionmixture was less than 3%. During the reaction, the aldehyde equivalentsin the reaction mixture were maintained at less than about 70% of thealdehyde equivalents in the total quantity of glyoxal to be charged formaking the condensation product. The reaction mixture was thendischarged from the reactor and comminuted, e.g., flaked. Properties ofthe polyphenol product of this example are given in tables which followand this example may be referred to as EX3.

EXAMPLE 4 (COMPARATIVE) PREPARATION OF PHENOL-GLYOXAL POLYPHENOL AT 102°AND REFLUX (103-104° C.) WITH ONE ADDITION OF GLYOXAL AND HCl CATALYST

To 576 g (6.12 moles) phenol and 6.23 g 18.5% HCl (0.2% HCl on phenol)at 90° C. is added over a one hour period 151.4 g of 40% glyoxal inwater (1.04 moles) while the temperature is allowed to rise to reflux(103-104° C.). The molar ratio of glyoxal to phenol was 0.17. After twohours at reflux about 93% of the aldehyde equivalents charged hadreacted. The reaction mixture was then vacuum distilled with thetemperature rising to 110° C. to remove aqueous HCl distillate of 116.4g. 100 g of hot water was then added to the reaction mixture anddistillation was continued at atmospheric pressure to 150° C. Thehydrochloric acid catalyst (HCl) is co-distilled with water from thereaction mixture. Then, by vacuum distillation up to 180°, the unreactedphenol was removed to less than 4% remaining in the reaction mixture.The reaction mixture is then discharged from the reactor and comminuted,e.g., flaked. Properties of the polyphenol product of this example aregiven in the tables which follow and this example may be referred to asEX4.

EXAMPLE 5 (COMPARATIVE) PREPARATION OF PHENOL-GLYOXAL POLYPHENOL AT 102°C. AND REFLUX (103-104° C.) WITH ONE ADDITION OF GLYOXAL ANDPHENOLSULFONIC ACID CATALYST

To 576 g (6.12 moles) phenol and 5.76 g (grams) (1.5% based on phenol)of 65% phenolsulfonic acid at 90° C. as catalyst there is added over aone hour period 151.4 g of 40% glyoxal in water (1.04 moles). The moleratio of glyoxal to phenol is 0.17. The temperature of the reactionmixture is permitted to rise to reflux (103-104° C.) where it remainedfor several hours and the conversion of aldehyde equivalents was up toabout 96% of that charged. This is followed by neutralization of thecatalyst, cooling to 65° C. and washing with distilled water to removesalt. This is followed by atmospheric distillation to 160° C. and thenvacuum distillation at about 176° C. to reduce the quantity of unreactedphenol in the reaction mixture to about 1%. The reaction mixture iseventually comminuted, e.g., flaked.

EXAMPLE 5A (COMPARATIVE)

The procedure of the above Example 5 was followed but the phenolsulfonicacid was replaced by 1.25 g (0.22% based on phenol) of anhydrousmethanesufonic acid. Approximately 97% of the aldehyde equivalentscharged had reacted prior to neutralization of the catalyst.Essentially, equivalent properties, molecular weights, viscosities, and% of TPE is obtained. Properties of the phenol-glyoxal condensationproduct are given in tables which follow wherein this example may bereferred to as EX5A.

EXAMPLE 6 LARGE SCALE PRODUCTION OF PHENOL-GLYOXAL CONDENSATION PRODUCTIN THE MANNER OF EXAMPLE 1

The phenol-glyoxal condensation product of Example 6 was prepared insubstantially the same manner as Example 1 except that it was preparedon large scale equipment which can produce several hundred pounds ofproduct and was vacuum steam sparged at 190° C. to reduce phenol below0.1%. The percent insolubles were 0.04% for the phenol-glyoxalcondensation product of this example whereas other properties are givenin tables which follow wherein this example may be referred to as EX6.The test for insolubles was conducted by essentially dissolving 15 g(grams) of condensate in 285 mls (milliliters) of isopropanol, filteringthrough a No. 42 Whatman filter paper and then drying the paper in anoven at 75° C. to 100° C. for 30 minutes.

EXAMPLE 7 LARGE SCALE PRODUCTION OF PHENOL-GLYOXAL CONDENSATION PRODUCTIN THE MANNER OF EXAMPLE 1

The phenol-glyoxal condensation product of Example 7 was prepared in thesame manner as that of Example 6, except that it was prepared at adifferent time. The percent insolubles in the product were 0.01% whereasother properties are given in tables which follow wherein this examplemay be referred to as EX7. The test for insolubles was performed in thesame manner as in Example 6 above.

EXAMPLE 8 PREPARATION OF POLY GLYCIDYL ETHER RESIN (EPOXY RESIN)

A one liter flask was charged with: 75 g (grams) of the flaked reactionproduct of Example 6; 200 g of isopropyl alcohol; and 52.5 g of water toform a reaction mixture. The reaction mixture was heated to 55° C. After10 minutes there was add 388.5 g of epichlorohydrin. The reactionmixture was reheated to 55° C. and then 30 g of a 20% solution of sodiumhydroxide in water was added while maintaining a temperature of 55° C.The 55° C. temperature was held for another 30 minutes. Then there wasadded 90 g of 20% solution of sodium hydroxide in water. The reactionmixture was held at 55° C. for another hour, heated to 65° C. and heldfor 30 minutes and then transferred to a separatory funnel. The upperclear brown organic layer (145.6 g) was stirred with 150 g water and 50g of dry ice. The aqueous layer was discarded and the organic layerwashed a second time and then vacuum distilled to recover excessepichlorohydrin and 105 g of dark resin of the epoxidized product ofExample 6. This epoxy resin has a weight per epoxy equivalent of 203.1and 225.8. This compares with a weight per epoxy equivalent of 210 forEPON 1031. Viscosities and weight per epoxy equivalent (WPE) of theepoxy resin of this Example 8 as well as comparisons with other epoxyresins prepared from polyphenols are shown below in tables wherein thisexample may be referred to as EX8.

EXAMPLE 9 (COMPARATIVE) PREPARATION OF PHENOL-GLYOXAL POLYPHENOL USINGACIDIC (SULFONIC ACID) ION EXCHANGE RESIN

To 709.3 g of phenol (7.54 moles) and 35.5 g of Amberlyst 15 which is adry sulfonic acid ion exchange resin sold by Rohm & Haas Co. at atemperature of 90° C. over 30 minutes, there was added 93 g of 40%glyoxal in water (0.64 moles). This resin was chosen since the resinused as catalyst in U.S. Pat. Nos.: 5,012,016; 5,146,006; and 5,191,128,all to S. Li, were unavailable and this resin appeared to be the closestto such resin. The temperature was maintained at 90° C. for another 1.5hours. After such time 88% of the aldehyde equivalents charged to thereaction mixture had reacted. Then there was vacuum distilled 42 g ofdistillate. On completion of the distillation 95% of the aldehydeequivalents charged to the reaction mixture had reacted. Another 93 g of40% glyoxal in water was added over 31 minutes while the temperature wasmaintained at 90° C. for 1.5 hours. After such 1.5 hours, 81% of thealdehyde equivalents charged to the reaction mixture had reacted. Thenthere was vacuum distilled 70 g of distillate at 90° C. over a period of30 minutes. The temperature of 90° C. was maintained for another 30minutes after which time, 91% of the aldehyde equivalents charged to thereaction mixture had reacted. The molar ratio of glyoxal to phenol forthe total of both glyoxal additions was 0.17. Catalyst was allowed tosettle and relatively clear liquor (687 g) decanted off and neutralizedto pH of 6 with 2.6 g of 50% sodium hydroxide. 650 g of neutralizedsolution was charged to a flask for atmospheric distillation to 160° C.The reaction mixture was then vacuum distilled to 175° C. to removephenol. During the reaction, the aldehyde equivalents in the reactionmixture were maintained at less than about 70% of the aldehydeequivalents in the total quantity of glyoxal to be charged for makingthe polyphenol. Yield of product was 263 g. The resulting polyphenol wasthen comminuted, e.g., flaked. Properties of the polyphenol are given intables which follow wherein this example may be referred to as EX9.

EXAMPLE 10 PREPARATION OF PHENOL-GLYOXAL CONDENSATION PRODUCT WITH TWOADDITIONS OF GLYOXAL, OXALIC ACID CATALYST AND TOTAL GLYOXAL/PHENOL MOLERATIO OF 0.22 FOR FIRST PORTION AND ADDITION OF PHENOL TO REDUCE THEGLYOXAL/PHENOL MOLE RATIO TO 0.17 FOR SECOND PORTION.

To 1419 g (15 moles) phenol and 56.5 g oxalic acid dihydrate at 90° C.there was added over 30 minutes 240 g of 40% glyoxal in water (1.655moles). The temperature was maintained at 90° C. for another 1.5 hoursand then there was vacuum distilled 148.3 g of distillate from thereaction mixture at 90° C. over a period of fifty minutes whereuponabout 62% of the aldehyde equivalents charged to the reaction mixturehad reacted after such fifty minute period. Another 240 g of 40% glyoxalin water (1.655 moles) was added to the reaction mixture over a 22minute period while the temperature was maintained at 90° C. for 1.5hours. About 58% of the aldehyde equivalents charged to the reactionmixture had reacted after this 1.5 hour period. There was then vacuumdistilled 212.2 g of distillate at 90° C. over a period of 45 minutes.After such 45 minute period about 65% of the aldehyde equivalentscharged to the reaction mixture had reacted. The molar ratio of glyoxalto phenol for the total of all the glyoxal additions was 0.22. Thetemperature of 90° C. was maintained for another 5 hours. After such 5hour period about 87% of the aldehyde equivalents charged to thereaction mixture had reacted. Then the reaction mixture was divided intotwo. To one half (794 g) was added 214 g of phenol to adjustglyoxal/phenol mole ratio to 0.17. The reaction mixture with addedphenol was heated at 90° C. for 2.5 hours whereupon 89% of the aldehydeequivalents charged to the reaction mixture had reacted. Percent waterin the reaction mixture was 4.9%. The reaction mixture was then heatedto 160° C. over 25 minutes and held at 160° C. for one hour, after whichthe bulk of phenol was removed by vacuum distillation to 175° C. Theproduct was then discharged from the flask. The remaining one-half ofreaction mixture without added phenol was heated to 160° C. as above andphenol removed by vacuum distillation to 175° C. The phenol-glyoxalcondensation product made with the 0.22 mole ratio of glyoxal to phenolis referred to in the tables as EX10.22 whereas that made with the 0.17mole ratio of glyoxal to phenol is referred to in the tables as EX10.17During the reaction, for both EX10.17 and EX10.22, the aldehydeequivalents in the reaction mixture were maintained at less than about70% of the aldehyde equivalents in the total quantity of glyoxal to becharged for making the phenol-glyoxal condensation product. Propertiesof the polyphenols are given in tables which follow. The polyphenol ofEX10.17 and that of EX10.12 were further heated at 190° C. for one hourunder full vacuum. Properties of these products are shown in thefollowing tables wherein the heated sample of EX10.17 is referred to asEX10.17H and that of EX10.22 is referred to as EX10.22H. It can be seenfrom the tables that the heated samples show improved opticalproperties.

EXAMPLE 11 PREPARATION OF PHENOL-GLYOXAL CONDENSATION PRODUCT WITH TWOADDITIONS OF GLYOXAL, GLYOXAL-PHENOL MOLE RATIO OF 0.17 WITHTRICHLOROACETIC ACID CATALYST AND USE OF BASIC MATERIAL IN REMOVAL OFHCL.

To 709.3 g (7.54 moles) phenol and 17.7 g trichloroacetic acid (2.5%based on the weight of phenol charged) at 90° C. there was added over 27minutes 92.9 g of 40% glyoxal (0.64 moles) in water. The temperature wasmaintained for 1.5 hours and about 58% of aldehyde equivalents hadreacted after such 1.5 hours. Subsequently, there was vacuum distilled62.2 g of distillate from the reaction mixture at 90° C. over 26minutes. After distillation, the aldehyde equivalents reacted(converted) was 70% of that charged and residual water content of thereaction mixture was about 3.5% Another 92.9 g of 40% glyoxal (0.64moles for a total of 1.28 moles) was added over half an hour while thetemperature was maintained for 1.5 hours. The total mole ratio ofglyoxal to phenol in this example was 0.17. After such heating about 62%of aldehyde equivalents charged to the reaction mixture had reacted.Subsequently there was vacuum distilled 81.6 g of distillate at 90° C.over 25 minutes. After the distillation, the aldehyde equivalentsconverted was 72% of that charged and the residual water in the reactionmixture was 3.5%. The temperature was maintained at 90° C. for another1.5 hours and about 88% of the aldehyde equivalents charged had reactedafter such 1.5 hour period. One half hour later 1.0 g of pyridine wasadded. At such time 88 percent of aldehyde equivalents which had beencharged to the reaction mixture had reacted. The temperature was raisedto 125° C. over one half hour and held at this temperature for 70minutes and further raised to 160° C. for 1.5 hours and held at thistemperature for 23 minutes to complete decomposition of acid. Thephenol-glyoxal condensation product was further heated at 190° C. forone hour under full vacuum to remove unreacted phenol and prepare thephenol-glyoxal condensation product which is also referred to as EX11 inthe following tables.

During the reaction, the aldehyde equivalents in the reaction mixturewere maintained at less than about 70% of the aldehyde equivalents inthe total quantity of glyoxal to be charged for making thephenol-glyoxal condensation product.

EXAMPLE 12 (COMPARATIVE) PREPARATION OF PHENOL-GLYOXAL CONDENSATIONPRODUCT WITH TWO ADDITIONS OF GLYOXAL, GLYOXAL-PHENOL MOLE RATIO OF 0.17WITH TRICHLOROACETIC ACID CATALYST WITHOUT USE OF BASIC MATERIAL INREMOVAL OF HCL.

The procedure of Example 11 was followed except that: a basic material,e.g., pyridine, was not added to the reaction mixture prior to raisingthe temperature to 125° C. and removal of the catalyst; and the finaltemperature after removal of phenol was 175° C. Processing of thisexample was discontinued upon heating to 175° C. because the viscositywas unduly high. This example is also referred to in the tables as EX12.

TABLE 1 CHARACTERIZATION OF SOME PHENOL-GLYOXAL POLYPHENOLS Mol WgtPhenol, TPE, Viscosity EX Mw/Mn % % cps(175° C.)  1 451/331 0.15 4.15480  2 464/347 0.29 5.10 510 (465/362)^((a))  3 468/351 2.05 8.53  300* 4 572/387 3.46 13.21  900*  5A 538/376 1.13 10.1 891  6 494/353 0.041.73 530  7 508/358 0.04 2.74 670  9 475/356 0.19 10.42 2,400   10.17485/348 3.80 5.5  350* 10.17H 496/357 <0.05 5.79 1088  10.22 518/3643.88 5.60  400* 10.22H 528/366 <0.05 4.83 1700  11 518/363 0.3 4.852040  12 552/357 0.30 1.02 >9,000     ^((a))value before catalyst wasremoved. These examples have a high phenol content which depresses theviscosity.

It can be seen from the above Table 1 that Examples 1, 6 and 7 gave thelowest percentage of TPE even though Examples 1-3 used the same catalystand the same mole ratio of reactants. The conventional catalysts such asHCl (EX4), sulfonic acid (EX5A and 9 give very high levels of TPE andeven oxalic acid when not used with incremental additions of glyoxal andremoval of distillates also gave a high value of TPE (EX3). The postheating at 190° C. in Examples 10.17H and 10.22H show no significanteffect on molecular weight or free TPE but decreased in free phenolcontent and increased in viscosity.

TABLE 2 FLUORESCENCE DATA OBTAINED OF 0.05% SOLUTION OF THE POLYPHENOLOR EPOXIDIZED POLYPHENOL IN TETRAHYDROFURAN (THF) AT ACQUISITION TIME OFONE SECOND AND AT AN EXCITATION WAVELENGTH OF 442 NM Example or MaximumIntensity Wavelength Product Counts Maximum, nm 1 11232 526 5A 6516 5326 11502 538 7 10535 532 EPON 1031* 6403 528 *EPON 1031 (CAS No.:7328-97-4) is a polyphenol containing tetraglycidyl ether of tetrakis(hydroxyphenyl)ethane and is sold by Shell Oil Co. of Emeryville, CA.

It can be seen from Table 2 above that Examples 1, 6 and 7 which arephenol-glyoxal condensation products of this invention had afluorescence which was about 70% higher than Example 5A which wasprepared with sulfonic acid catalyst. Similar results are shown inTables 3 and 4 which follow.

TABLE 3 FLUORESCENCE OF 0.05% SOLUTION OF EPOXIDIZED POLYPHENOL IN THFAT EXCITATION WAVELENGTH OF 442 NM AND ACQUISITION TIME OF 1.0 SECONDMaximum Intensity Wavelength Material Counts Maximum, nm EPON 1031 9640527 EX8 14,600 535

It can be seen from the above Table 3 that the product of Example 8,namely the epoxidized product of Example 6, shows about 50% morefluorescence than the commercial product EPON 1031.

TABLE 4 FLUORESCENCE DATA OBTAINED OF 0.05% SOLUTION OF THE POLYPHENOLIN TETRAHYDROFURAN (THF) AT ACQUISITION TIME OF ONE SECOND AND AT ANEXCITATION WAVELENGTH OF 442 NM WITH THE DATA OF THIS TABLE 4 BEINGOBTAINED ON A DIFFERENT DATE FROM THAT OF TABLES 2 AND 3. Concentrationwt. % Maximum Intensity, Wavelength Example Of The Polyphenol CountsMaximum nm 1 0.0500 16640 530 1 0.0500 16300 531 2 0.0503 13550 530 20.0503 13510 529 3 0.0500 12860 536 3 0.0500 12640 532 4 0.0500 13960523 4 0.0490 13850 525 5A 0.050 9920 535 5A 0.050 9620 530 2* 0.04986940 540 3* 0.0501 5130 530 3* 0.0501 5280 527 5A* 0.0503 5010 530 *Thevalues for these are of the reaction mixture before removal of catalyst.

It can be seen from Table 4 above, that Example 1 has a fluorescencewhich is substantially higher than the other examples, includingExamples 2 and 3 which used the same catalyst in the same mole ratio ofreactants.

TABLE 5 ULTRA VIOLET (UV) ABSORBANCE DATA IN DILUTE TETRAHYDROFURAN (10MG/100 ML) Material At 350 nm At 365 nm Example 1 0.544 0.300 Example 20.470 0.258 Example 3 0.500 0.270 Example 5A 0.367 0.220 EP* of Example5A 0.290 0.168 Example 6 0.515 0.288 Example 8 0.400 0.223 Example 90.266 0.134 EX10.17 0.385 0.216 EX10.17H 0.416 0.224 EX10.22 0.418 0.239EX10.22H 0.470 0.258 EX11 0.728, 0.739 0.395, 0.404 EX12 0.465 0.317EPON 1031 0.273 0.161 Pure TPE 0.000 0.000 *Epoxy

It can be seen from the above Table 5 that Example 1 and Example 11afford the highest absorbance at both 350 and 365 nm. All of the oxalicacid catalyzed products gave higher absorbance as compared to thesulfonic acid catalyzed products of Examples 5A and 9. All other thingsbeing equal, the greater concentrations of TPE provide lower opticalproperties. Also, it should be noted that TPE shows no absorbance underthe test conditions. It can also be seen that the phenol-glyoxalcondensation products of Example 10 and Example 11 which were heated at190° C. for one hour, namely EX10.17H, EX10.22H, EX11.17H and EX11 hadbetter optical properties as compared to the product before suchheating, namely EX10.17, EX10.22, and EX11. Additionally, it can be seenthat the epoxidized product of Example 1, namely Example 8, gavesignificantly higher absorbance than the commercial product EPON 1031.Although the product of Example 12 showed high absorbance values, itsviscosity was unduly high, namely, over 9000 cps at 175° C. as shown inTable 1 above, and thus unacceptable.

TABLE 6 VISCOSITIES AND WEIGHT PER EPOXY EQUIVALENTS (WPE) MaterialMw/Mn Viscosity, cps WPE EPON1031 895/395 14880 (100° C.) 216 997 (125°C.) 172 (150° C.) EPOXY of 576/348 12210 (100° C.) 214 Example 61580(125° C.) 440 (150° C.) Epoxy of 767/374 11580 (100° C.) 233 Example5A 821 (125° C.) 142 (150° C.)

TABLE 7 FLUORESCENCE OBTAINED OF PRODUCTS IN 0.05% SOLUTION IN THF ATEXCITATION WAVELENGTHS OF 442 NM BUT AT ACQUISITION TIME OF ONE-HALF OFA SECOND. Counts at Maximum Wavelength Product of Intensity Maximum nmEX6 19,960 531 EX11 17,390 532 EX10.22 19,040 530 EX10.22H 19,940 530EX10.17H 20,120 530

TABLE 8 SOLUBILITY OF CONDENSATION PRODUCTS Solubility at 50% acetonewas attempted with the various phenol-glyoxal condensates. A large vial718 inches in internal diameter was charged with 10 g each of acetoneand solid, warmed with vigorous agitation and then allowed to settle for10 days at room temperature. The total height of the mixes was 1.75inches. The clear supernatant layer was measured and is reported belowin millimeters (mm). Lower values are indicative of lower solubility.Material Clear Liquor, mm EX1 32 EX2 28 EX4 8 EX5A 23 EX10.17 17 EX10.2222 EX6 41 EX9 7 EX11 24

Several materials were checked for 50% solubility in methyl ethylketone. The product of Examples 1-3 and 11 remained completely solubleat room temperature after standing 10 days. Product from Example 5Adeposited some product after standing 3 days.

TABLE 9 METAL ION CONTENTS OF POLYPHENOLS & EPON 1031 Metal EPON Ion EX1EX6 EX7 EX5A* 1031 Na 0.003 0.001 0.002 0.017 0.028 Ca 0.002 0.001 0.001<0.001 0.001 Fe <0.001 <0.001 0.001 <0.001 <0.001 K 0.008 <0.001 <0.001<0.001 0.001 *This is product of EX5A on large scale equipment

EXAMPLE 13 PREPARATION OF PREPREGS AND LAMINATES

Prepregs and laminates were made from the following resinous matrixformulation.

Material Percent by weight 1. Brominated epoxy resin (EPON 1124 60.0 A80of Shell Chemical) 2. Phenol-glyoxal condensate (PGC) 3.0 3. Phenolnovolac curing agent 14.4 (Durite SD1711 of Borden Chemical) 4. Acetone15.05 5. Methyl ethyl ketone 7.45 6. 2-methyl imidazole 0.2

Two solutions of 2,000 cps viscosity (25° C.) were made wherein twodifferent PGC's were used. The PGC's (phenol-glyoxal condensates) werethe epoxides (glycidylated derivatives) of Example 6 and Example 5A asshown in the Examples hereinabove. The epoxy of Example (Ex) 6 was madeby the process of Example 8 and the epoxy of Example 5A was made bysubstantially the same procedure. The two materials are characterizedbelow in Test 13A.

Test 13A Epoxy of Mw/Mn Viscosity, cps WPE Ex. 6 576/348 12210(100° C.)214 Ex. 5A 767/374 11580(100° C.) 233

Two-ply 11.5 inch square laminates of 7-8 mils thickness were made via ahand dip process using 2116 style glass (an E-glass) with a BGF 643finish. Cure conditions were typical for meeting the National ElectricalManufacturers' Association (NEMA) FR4 specification, namely, 1.5 minutesat 325-350° C. in an oven for the prepreg. The prepreg was then cooledto room temperature and heated over 45 minutes to 350° F., and then heldat this temperature for about 30 minutes before cooling to roomtemperature. The resin content for the laminates was about 60% byweight.

The laminates were then cut into 4 inch squares and inspected withmodern automatic optical inspection (AOI) equipment. In the case ofultraviolet absorbance, the following equipment can be used:Hewlett-Packard's HP BV 3000, Teradyne's 5539 and Orbitech's VT 8000.The results of the AOI for fluorescence are shown in Test 13B belowwherein the tests were carried out in duplicate or triplicate.

Test 13B Epoxy PGC in Fluorescence Dynamic Range Formulation IntensityNoise Level EX.6 epoxy 192.2 2.0 194.7 2.0 EX.5A epoxy 130.8 1.6 125.41.5 135.5 1.8

The data in Test 13B above show that the formulation using the epoxy ofExample 6 shows 48% higher fluorescence than the formulation using theepoxy of Example 5A.

Replacement of the epoxy of EX. 6 by unepoxidized material, i.e., thephenol-glyoxal condensation product of Example 6 in the laminatingformulation in comparison with the phenol-glyoxal condensate of example5A with the use of AOI as discussed above showed that the phenol-glyoxalcondensate of Example 6 increased the fluorescence over that obtainedwith Example 5A by about 50% to 70% and provided clearer images to theCCD (charged couple device) cameras of the AOI equipment. The brominatedepoxy for the above formulation can be partially or completely replacedby a bisphenol-A epoxy resin with comparable epoxy equivalent to obtainsimilar results.

The formulation of Example 13 is a preferred formulation. However, thebrominated epoxy resin can vary from about 40% to 80% by weight of theformulation, and such resin can be substituted with a different halogensuch as chlorine. Also, the epoxy resin need not be halogenated but iffire retardency is desired, such retardency can be obtained by theaddition of a conventional fire retardant. The phenol-glyoxal condensatecan vary in quantity from about 1% or 2% to about 15% and be substitutedentirely or partially with an equal quantity of a phenol-glyoxalresidue. The quantity of phenol novolac curing agent can vary from about7% to about 35% and the quantity of solvent system can vary from about10 to 35%, all percentages or parts being by weight.

EXAMPLE 14 FLUORESCENCE ANALYSIS IN COMPARISON WITH ACRIDINE ORANGE BASE

In this example, all spectra were collected using 0.05 wt. % solutionsof the samples in spectroscopic grade tetrahydrofuran (THF). Thesolutions were prepared by dissolving the solids in the necessary amountof THF to give the desired concentration. The standard Acridine OrangeBase (Aldrich Chemical Co. Milwaukee, Wis.) solution (0.78 μM) wasprepared by diluting an aliquot of a concentrated solution of the dye inmethanol. Concentration of the standard was confirmed by absorptionspectroscopy. CM 1000 equipment was set to provide 442-nanometerexcitation and measurements were taken using 0.5 second acquisitiontime. Table 14 presents the results of the measurements withfluorescence intensity reported in Counts per second as well as apercentage of the intensity of the standard at respective wavelength.

TABLE 14 RESULTS OF FLUORESCENCE ANALYSIS IN THE USING CM 1000 In thistable, the excitation wavelength was 442 nm; acquisition time was 0.5seconds and Concentration was 0.05 wt %. Intensity Relative to AcridineFluorescence Intensity Orange Base Sample Maximum, nm Counts/s Standard,% Acridine Orange Base 528 (maximum) 0.78 μM (0.2 mg/L) 524 23800 InMethanol 530 24000 532 23800 535 23400 Condensate of Ex 5A 532 24000 100Condensate of Ex 6 532 40600 170

What is claimed is:
 1. In a laminate comprising superimposed poroussubstrates impregnated with a resinous matrix comprising an epoxy resinand a curing agent for the epoxy resin; the improvement which comprisessaid resinous matrix containing from about 1 to 35 parts by weight of afluorescent polyphenol, said polyphenol being a member selected from thegroup consisting of a fluorescent phenol-glyoxal condensate, afluorescent residue of a phenol-glyoxal condensate and mixtures thereofwherein the condensate is produced from a monohydric phenol and glyoxalby a method comprising (a) charging phenol to a reaction vessel andincrementally charging a total of about 0.15 to 0.22 moles of glyoxalfor each mole of the phenol charged to the reaction vessel to form areaction mixture at a temperature of about 80° C. to 100° C. in thepresence of about 1% to 6%, based on the weight of phenol charged, of anacid catalyst which can be removed from the reaction mixture by heatingand distilling the reaction mixture at a temperature below about 170°C., said catalyst selected from the group consisting of oxalic acid,trichloroacetic acid and trifluoroacetic acid; (b) incrementallyremoving water from the reaction mixture; (c) maintaining the aldehydeequivalents in the reaction mixture at less than about 70% of thealdehyde equivalents in the total quantity of glyoxal to be charged formaking the condensation product; (d) distilling the reaction mixture ata temperature of less than about 170° C. to remove the acid catalystwhen at least 85% of the aldehyde egivalents in the total quantity ofglyoxal to be charged for making the condensation product have reacted,provided that prior to such distillation, a basic material is added tothe reaction mixture in an amount sufficient to neutralize hydrochloricacid when the catalyst is trichloroacetic acid; (e) heating the reactionmixture at a temperature of about 175° C. to 200° C. for about 0.25hours to 3 hours after step (d) above; and (f) removing unreacted phenolfrom the reaction mixture to obtain a phenol-glyoxal condensationproduct containing less than about 5% by weight of phenol.
 2. Thelaminate of claim 1 wherein the curing agent is a phenol-formaldehydenovolac resin and the quantity of said fluorescent polyphenol is fromabout 1 to 15 parts.
 3. The laminate of claim 2 wherein the fluorescentpolyphenol is a phenol-glyoxal condensate.
 4. A laminate having improvedfluorescence, said laminate comprising a reinforcing agent and aresinous matrix wherein the matrix contains: (a) an epoxy resin; (b) acuring agent for the epoxy resin; and (c) about 1 to 35 parts of amember selected from the group consisting of, (i) a phenol-glyoxalcondensate; (ii) a glycidylated phenol-glyoxal condensate; (iii) areaction product of about 4 to 8 parts of a glycidyl epoxy resin foreach part of a phenol-glyoxal condensate; and (iv) mixtures thereof, allof said parts being by weight wherein the epoxy resin, curing agent, theitems (i) (ii), (iii) and/or (iv) comprise at least 75% of the resinousmatrix and wherein the condensate has a fluorescence which is at least25% higher than Acridine Orange Base at an excitation wavelength of 442nm and an acquisition time of 0.5 seconds when the Acridine Orange Baseis used at a concentration of 0.2 mg/liter in methanol and thephenol-glyoxal condensate is used at a concentration of 0.05 weightpercent in tetrahydrofuran and not more than 6% of a tetraphenol ethane.5. The cured laminate of claim
 4. 6. The laminate of claim 4 wherein thephenol used to make the condensate is phenol itself and the quantity offree phenol in the condensate is from 0 to 5%.
 7. The laminate of claim4 wherein the cured laminate contains from about 40 to 80 parts byweight of an epoxy resin and the phenol is a monohydric mononuclearphenol having from 6 to 12 carbon atoms.
 8. A porous substrateimpregnated with about A. 40 to 80 parts by weight of an epoxy resin; B.about 7 to 35 parts by weight of a phenol-formaldehyde novolac; C. about1 to 15 parts by weight of a highly fluorescent material selected fromthe group consisting of: (a). a phenol-glyoxal condensate; (b). theresidue of a phenol-glyoxal condensate; and (c) mixtures of saidcondensate and residue; D. about 10 to 35 parts by by weight of asolvent system for the epoxy resin and the novolac; and E. anaccelerator for curing the resin mixture wherein the condensate: (1) hasa fluorescence which is at least 25% higher than Acridine Orange Base atan excitation wavelength of 442 nm and an acquisition time of 0.5seconds when the Acridine Orange Base is used at a concentration of 0.2mg/liter in methanol and the phenol-glyoxal condensate is used at aconcentration of 0.05 weight percent in tetrahydrofuran; (2) is of amonohydric mononuclear phenol having from 6 to 12 carbon atoms, (3) andcontains not more than 6% of a tetraphenol ethane.
 9. A process forpreparing resin impregnated substrates for use in preparing electricallaminates which process comprises impregnating said substrates with animpregnating composition comprising: A. An epoxy resin having a weightper epoxide value of from about 190 to 2,000; B. a curing agent for theepoxy resin; C. a solvent system for components A and B; then D. heatingthe resulting impregnated substrate to B stage resin and removing thesolvent system; the improvement which comprises including in theimpregnating composition from about 1 to 15 parts by weight of theimpregnating composition a member selected from the group consisting of,(a) fluorescent polyphenol of a phenol and glyoxal; (b) a fluorescentresidue of a polyphenol of a phenol and glyoxal; and (c) mixtures of (a)and (b) wherein the polyphenol has a fluorescence which is at least 25%higher than Acridine Orange Base at an excitation wavelength of 442 nmand an acquisition time of 0.5 seconds when the Acridine Orange Base isused at a concentration of 0.2 mg/liter in methanol and thephenol-glyoxal condensate is used at a concentration of 0.05 weightpercent in tetrahydrofuran and said condensate contains not more than 6%of tetraphenol ethane.
 10. The process of claim 9 wherein the epoxyresin has a weight per epoxide value of from about 190 to about 500, thepolyphenol contains not more than 4.15% of a tetraphenol ethane and andthe phenol of the polyphenol is phenol itself.
 11. A cured laminateprepared by pressing together and heating multiple plies of theimpregnated substrates of claim
 9. 12. A laminate comprisingsuperimposed porous substrates impregnated with a resinous matrixwherein said resinous matrix comprises: A. About 40 to 80 parts byweight of an epoxy resin having a weight per epoxide value of about 190to about 10,000 B. About 7 to 35 parts by weight of a curing agent forthe epoxy resin; the improvement which comprises including in theresinous matrix from about 1 to 15 parts of a fluorescent polyphenolsaid polyphenol being a member selected from the group consisting of aphenol-glyoxal condensate, the residue of a phenol-glyoxal condensatewherein such residue is that of a glycidylated phenol-glyoxal condensateor the reaction product of a polyepoxide and said phenol-glyoxalcondensate and mixtures of said condensate and residue, said condensateprepared by: (a) charging, to a reaction vessel, a monohydric,mononuclear phenol having up to 12 carbon atoms and from about 0.06 to0.11 moles of a 40% solution of glyoxal in water, the quantity ofglyoxal based on the moles of phenol charged, to form a reaction mixtureand wherein the reaction mixture is at a temperature of about 80° C. to100° C. in the presence of about 3 to 5% of oxalic acid; (b) conductinga first distillation of the reaction mixture at said reactiontemperature after about 1 to 5 hours from initial reaction of the phenolwith the glyoxal in the reaction mixture and removing about 8% to 12% byweight of distillate, based on the quantity of phenol charged, from thereaction mixture; (c) charging to the reaction mixture another 0.06 to0.11 moles of the glyoxal based on the moles of phenol charged whereinthe total quantity of glyoxal charged to the reaction mixture is fromabout 0.15 to 0.22 moles of glyoxal for each mole of the phenol chargedand continuing the reaction at the said reaction temperature for aboutanother 1.5 to 6 hours after the commencement of the first distillationand then conducting a second distillation of the reaction mixture at thesaid reaction temperature to remove from about another 4% to 12% byweight of distillate based on the quantity of phenol charged; (d)continuing the reaction after the second distillation at the reactiontemperature until at least 85% of the aldehyde equivalents of the totalquantity of glyoxal to be charged for making the condensation producthave reacted; (e) raising the temperature above about 130° C. to about170° C. and distilling the reaction mixture to eliminate the catalyst;(f) heating the reaction mixture at a temperature of about 175° C. to200° C. for about 0.25 hours to 3 hours after removal of the catalyst;and (g) removing unreacted phenol to recover a phenol-glyoxalcondensation product containing not more than about 5% of unreactedphenol.
 13. The laminate of claim 12 wherein the epoxy resin has aweight per epoxide value of about 190 to about
 500. 14. The laminate ofclaim 12 wherein the curing agent is a phenol-formaldehyde novolacresin, the resinous matrix contains a curing accelerator and themononuclear phenol for preparing the condensate is phenol itself.
 15. Ina laminate comprising superimposed porous substrates impregnated with anuncured resinous matrix comprising an epoxy resin and a curing agent forthe epoxy resin; the improvement which comprises said resinous matrixcontaining from about 1 to 15 parts by weight, based on the weight ofthe epoxy and curing agent of a polyphenol, said polyphenol being afluorescent phenol-glyoxal condensate having an ultraviolet absorbanceof at least 0.260 at 365 nm and/or 0.400 at 350 nm and a fluorescencewhich is at least 25% higher than Acridine Orange Base, at an excitationwavelength of 442 nm and an acquisition time of 0.5 seconds when theAcridine Orange Base is used at a concentration of 0.2 mg/liter inmethanol and the phenol-glyoxal condensate is used at a concentration of0.05 weight percent in tetrahydrofuran.
 16. The cured laminate of claim15 wherein the resinous matrix includes a fire retardant.
 17. The curedlaminate of claim 15 wherein the resinous matrix includes a sufficientquantity of a halogenated epoxy resin to render the laminate fireretardant.
 18. The laminate of claim 17 wherein the halogenated epoxyresin is a brominated epoxy resin.
 19. A laminate of reinforcing fibersin a resinous matrix containing from 1 to 35 parts by weight of a memberselected from the group consisting of a glycidylated phenol-glyoxalcondensate, a phenol-glyoxal condensate and mixtures thereof whereinsaid phenol-glyoxal condensate prior to glycidylation contains not morethan 4.15% of a tetraphenol ethane.
 20. The cured laminate of claim 19wherein prior to curing the condensate contains from 0 to 5% of a freephenol.
 21. The laminate of claim 19 wherein the phenol is phenolitself.
 22. A laminate of reinforcing fibers in a resinous matrixcomprising an epoxy resin and a curing agent for the epoxy resin whereinthe matrix contains from 1 to 35 parts by weight of a fluorescent memberselected from the group consisting of (a) a polyphenol of a phenol andglyoxal, a residue of a polyphenol of a phenol and glyoxal and mixturesthereof wherein the polyphenol contains not more than 4.15% of atetraphenol ethane.
 23. The laminate of claim 22 wherein the member is apolyphenol of a phenol and glyoxal.
 24. The laminate of claim 23 whereinthe phenol is phenol itself.
 25. The cured laminate of claim 24 whereinthe polyphenol, prior to curing, has a viscosity of 300 to 2,500 cps at175° C. and a free phenol content of 0 to 5%.